1. Field of the Invention
The invention generally relates to a breaker mechanism for a power circuit breaker in a die cast housing, the circuit breaker being connected with a crossbar supporting contact arms. The breaker mechanism contains a connecting element, a bracing lever which can be driven with the connecting element two toggle levers connected on their terminal ends, an energy storage mechanism engaged between the connecting element and the ends of the toggle levers, a latch which can be activated by trips, and a latch lever which can be latched by the latch and which, for its part, locks the bracing lever in the untripped position.
2. Background Information
Generally, a breaker mechanism, as a mechanical link equipped with an energy storage mechanism between the manual activation mechanism or the mechanical drive and the contact system, is used for closing and opening, as well as automatic tripping when overcurrents occur.
A known breaker mechanism is disclosed in German Laid Open Patent Application No. 38 12 950 and mounted in a die-cast, or molded, housing of the power circuit breaker and contains a connecting element which can be activated by means of a grip handle. The grip handle is mounted so that it can pivot in a U-shaped frame. The breaker mechanism also contains a bracing lever linked by means of a fastening block to the frame, as well as toggle levers connected to the bracing lever on both sides, with a roller on their ends. The roller is used to pivot, by means of crossbar cam slots, a crossbar supporting a contact arm and simultaneously to engage two toggle lever springs which are under tension and which are fastened to the switch connecting element and act as energy storage mechanisms. On the open side of the support frame, there is a side frame, in which a latch lever and a latch are mounted so that they can pivot, along with a leaf-shaped latch spring. In the closed and open positions, the bracing lever is locked by means of a hook through the latch lever, which for its part is latched by means of correspondingly configured latching surfaces by the latch. If, by means of a thermal or a magnetic overcurrent trip, the latch is caused to pivot, then the latching surfaces are released. Under the action of the force exerted by the toggle lever springs, the latch, the bracing lever which is thereby unlocked, the toggle levers and the connecting elements are rocked into the tripped position, i.e. opening the contacts. After the cause of the trip has been eliminated, the breaker mechanism can be relatched or relocked and closed, via the open position.
One disadvantage of the known solution described above is that it costs too much to manufacture. It is expensive in particular because of the requirement for the side frame and the fastening block which, like the latch, must generally be manufactured in a complex, time-consuming and expensive manner as die cast parts. It also requires a great many mounting means, such as: rivets for the connection between the bracing lever and the toggle; pivots for the bracing lever, the side frames and the latch; as well as an alignment pin and guide hole for the fastening block. Because of the use of the complex actuator roller, specially designed latch springs and two toggle springs are also required. An additional significant disadvantage is that if the contacts weld shut, the contact apparatus may not open in spite of the tripping of the breaker mechanism.